Short range projectile weapons, for example pistols, shotguns and crossbows, typically have a lower barrel velocity than a rifle, resulting in significant variation in bullet drop, dependent on range, even at a relatively short range, for example 50 yards. The reflex sights typically used to aid a shooter in aiming such a firearm, however, only permit a single indicator of where a bullet will hit, thereby requiring a shooter to form a mental estimate of the hitting point for a range different from that for which the reticle position has been set.
Also, there is a fair amount of uncertainty in the angle at which a projectile will leave the weapon, or for a shotgun, the area over which pellets will hit. There are currently limited options for assisting a shooter in forming an estimate of an area over which a projectile is likely to hit, or shotgun pellets will hit. Conversely, there are limited options for determining where a bullet will quite certainly not hit, so that it may be difficult at times to estimate potential collateral damage.